Bottom Line:
DWI was successfully obtained in all patients.Similar results were obtained when the two observers were analyzed separately (observer 1: p = 0.006, observer 2: p = 0.04).In this pilot study, on a patient-friendly 1.0-T open-bore MRI, we demonstrated that DWI may potentially be a feasible non-invasive imaging technique in children with JIA.

Objective: To evaluate the feasibility of non-invasive diffusion-weighted imaging (DWI) of the knee of children with juvenile idiopathic arthritis (JIA) and, further, to analyze the apparent diffusion coefficient (ADC) levels to distinguish synovium from effusion.

Materials and methods: Standard magnetic resonance imaging of the knee including post-contrast imaging was obtained in eight patients (mean age, 12 years 8 months, five females) using an open-bore magnetic resonance imaging system (1.0 T). In addition, axially acquired echo-planar DWI datasets (b-values 0, 50, and 600) were prospectively obtained and the diffusion images were post-processed into ADC50-600 maps. Two independent observers selected a region of interest (ROI) for both synovium and effusion using aligned post-contrast images as landmarks. Mann-Whitney U test was performed to compare ADC synovium and ADC effusion.

Results: DWI was successfully obtained in all patients. When data of both observers was combined, ADC synovium was lower than ADC effusion in the ROI in seven out of eight patients (median, 1.92 × 10(-3) mm(2)/s vs. 2.40 × 10(-3) mm(2)/s, p = 0.006, respectively). Similar results were obtained when the two observers were analyzed separately (observer 1: p = 0.006, observer 2: p = 0.04).

Conclusions: In this pilot study, on a patient-friendly 1.0-T open-bore MRI, we demonstrated that DWI may potentially be a feasible non-invasive imaging technique in children with JIA. We could differentiate synovium from effusion in seven out of eight patients based on the ADC of synovium and effusion. However, to select synovium and effusion on DWI, post-contrast images were still a necessity.

Mentions:
All diffusion-weighted images were post-processed into ADC50–600 maps on the MRI console computer. The ADC50–600 map was chosen to prevent signal from vascular flow to influence the ADC values [23, 24]. For further analysis, in-house-developed software using MATLAB version R2011b (The MathWorks Inc., Natick, MA, USA) was used to assess diffusion. On the ADC maps, a region of interest (ROI) was drawn in a region where synovium was present as demonstrated by CE MRI (Fig. 1), the second ROI was drawn in an area with effusion (Fig. 2). Two independent readers selected ROI (C.M.N., 3 years of experience in musculoskeletal imaging and R.H., 6 years of experience in musculoskeletal imaging). ROI selection on the ADC50–600 maps was performed while aligning the post-contrast images to the diffusion-weighted images to ensure correct selection of synovium or effusion as displayed in Figs. 1 and 2. For final confirmation, the ADC maps with ROIs and post-contrast images were discussed under supervision of M.M. (19 years of experience in musculoskeletal imaging); all ROIs were approved. Lastly, mean ADC and standard deviation (SD) of the ROIs were extracted by MATLAB.Fig. 1

Mentions:
All diffusion-weighted images were post-processed into ADC50–600 maps on the MRI console computer. The ADC50–600 map was chosen to prevent signal from vascular flow to influence the ADC values [23, 24]. For further analysis, in-house-developed software using MATLAB version R2011b (The MathWorks Inc., Natick, MA, USA) was used to assess diffusion. On the ADC maps, a region of interest (ROI) was drawn in a region where synovium was present as demonstrated by CE MRI (Fig. 1), the second ROI was drawn in an area with effusion (Fig. 2). Two independent readers selected ROI (C.M.N., 3 years of experience in musculoskeletal imaging and R.H., 6 years of experience in musculoskeletal imaging). ROI selection on the ADC50–600 maps was performed while aligning the post-contrast images to the diffusion-weighted images to ensure correct selection of synovium or effusion as displayed in Figs. 1 and 2. For final confirmation, the ADC maps with ROIs and post-contrast images were discussed under supervision of M.M. (19 years of experience in musculoskeletal imaging); all ROIs were approved. Lastly, mean ADC and standard deviation (SD) of the ROIs were extracted by MATLAB.Fig. 1

Bottom Line:
DWI was successfully obtained in all patients.Similar results were obtained when the two observers were analyzed separately (observer 1: p = 0.006, observer 2: p = 0.04).In this pilot study, on a patient-friendly 1.0-T open-bore MRI, we demonstrated that DWI may potentially be a feasible non-invasive imaging technique in children with JIA.

Objective: To evaluate the feasibility of non-invasive diffusion-weighted imaging (DWI) of the knee of children with juvenile idiopathic arthritis (JIA) and, further, to analyze the apparent diffusion coefficient (ADC) levels to distinguish synovium from effusion.

Materials and methods: Standard magnetic resonance imaging of the knee including post-contrast imaging was obtained in eight patients (mean age, 12 years 8 months, five females) using an open-bore magnetic resonance imaging system (1.0 T). In addition, axially acquired echo-planar DWI datasets (b-values 0, 50, and 600) were prospectively obtained and the diffusion images were post-processed into ADC50-600 maps. Two independent observers selected a region of interest (ROI) for both synovium and effusion using aligned post-contrast images as landmarks. Mann-Whitney U test was performed to compare ADC synovium and ADC effusion.

Results: DWI was successfully obtained in all patients. When data of both observers was combined, ADC synovium was lower than ADC effusion in the ROI in seven out of eight patients (median, 1.92 × 10(-3) mm(2)/s vs. 2.40 × 10(-3) mm(2)/s, p = 0.006, respectively). Similar results were obtained when the two observers were analyzed separately (observer 1: p = 0.006, observer 2: p = 0.04).

Conclusions: In this pilot study, on a patient-friendly 1.0-T open-bore MRI, we demonstrated that DWI may potentially be a feasible non-invasive imaging technique in children with JIA. We could differentiate synovium from effusion in seven out of eight patients based on the ADC of synovium and effusion. However, to select synovium and effusion on DWI, post-contrast images were still a necessity.